Proxying read requests when performance or availability failure is anticipated

ABSTRACT

A method includes receiving, by a read threshold number of storage units of a dispersed storage network (DSN), the read threshold number of read requests regarding the read threshold number of encoded data slices of a set of encoded data slices. The method further includes determining, by each storage unit of the read threshold number of storage units, whether the storage unit is capable of processing a respective read request. When a particular storage unit is not capable of processing the respective read request, the method further includes sending, by the particular storage unit, a proxy read request to another storage unit that is not in the read threshold number of storage units. The method further includes determining, by the other storage unit, whether the other storage unit is capable of processing the proxy read request and, when it is, processing the proxy read request.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §119(e) to U.S. Provisional Application No. 62/314,792,entitled “SELECTING A PROCESSING UNIT IN A DISPERSED STORAGE NETWORK,”filed Mar. 29, 2016, which is incorporated herein by reference in itsentirety and made part of the present U.S. Utility Patent Applicationfor all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

DESCRIPTION OF RELATED ART

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.It is further known that storage units within a dispersed storage systemmay fail or require maintenance from time to time. To efficientlyprocess user requests, storage unit failures or lag times should beanticipated and addressed within the system.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of an embodiment of sending a proxyread request within a dispersed storage network (DSN) in accordance withthe present invention; and

FIG. 10 is a logic diagram of an example of a method of sending a proxyread request within a dispersed storage network (DSN) in accordance withthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 and 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data (e.g., data 40) as subsequently described withreference to one or more of FIGS. 3-8. In this example embodiment,computing device 16 functions as a dispersed storage processing agentfor computing device 14. In this role, computing device 16 dispersedstorage error encodes and decodes data on behalf of computing device 14.With the use of dispersed storage error encoding and decoding, the DSN10 is tolerant of a significant number of storage unit failures (thenumber of failures is based on parameters of the dispersed storage errorencoding function) without loss of data and without the need for aredundant or backup copies of the data. Further, the DSN 10 stores datafor an indefinite period of time without data loss and in a securemanner (e.g., the system is very resistant to unauthorized attempts ataccessing the data).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The managing unit 18 creates and stores user profile information (e.g.,an access control list (ACL)) in local memory and/or within memory ofthe DSN memory 22. The user profile information includes authenticationinformation, permissions, and/or the security parameters. The securityparameters may include encryption/decryption scheme, one or moreencryption keys, key generation scheme, and/or data encoding/decodingscheme.

The managing unit 18 creates billing information for a particular user,a user group, a vault access, public vault access, etc. For instance,the managing unit 18 tracks the number of times a user accesses anon-public vault and/or public vaults, which can be used to generate aper-access billing information. In another instance, the managing unit18 tracks the amount of data stored and/or retrieved by a user deviceand/or a user group, which can be used to generate a per-data-amountbilling information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (TO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the I0 deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment (i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 80 is shown inFIG. 6. As shown, the slice name (SN) 80 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

FIG. 9 is a schematic block diagram of an embodiment of sending a proxyread request within a dispersed storage network (DSN). The DSN of FIG. 9includes a DS client module 34 of a computing device and a set ofstorage units (SU #1-SU #8) storing a set of encoded data slices (EDS1_1-EDS 8_1). A data segment of a data object is dispersed storage errorencoded into the set of encoded data slices (EDS 1_1-EDS 8_1).

In an example of operation, a read threshold number of storage units ofthe set of storage units (SU #1-SU #5), receive a read threshold numberof read requests 82 from the DS client module 34. The read thresholdnumber of read requests 82 is regarding the read threshold number ofencoded data slices of a set of encoded data slices. The read thresholdnumber is a number of encoded data slices per set and is less than atotal number of encoded data slices in the set and is equal to orgreater than the decode threshold number. In this example, the totalnumber of encoded data slices in the set is 8, the read threshold numberis 5, and the decode threshold number is 4.

Each storage unit of the read threshold number of storage units(SU#1-SU#5) determines whether it is capable of processing a respectiveread request of the read threshold number of read requests 82. Forexample, a storage unit of the read threshold number of storage unitsdetermines that it is not capable of processing the respective readrequest when it determines that it does not currently store an encodeddata slice identified in the respective read request. The storage unitdetermines that it does not currently store an encoded data sliceidentified in the respective read request by one or more of: performinga table lookup, attempting to recover the encoded data slice from alocal memory, and attempting to recover the encoded data slice from anon-local memory. As another example, a storage unit determines that itis not capable of processing the respective read request when itdetermines that the encoded data slice identified in the respective readrequest is stored in one of its memory devices that is currentlyunavailable. In another example, the storage unit is unavailable due toa failure, it is being replaced and/or it is undergoing maintenance. Asa further example, a storage unit determines that it cannot process therespective read request within a response time threshold.

When a particular storage unit is not capable of processing therespective read request, it sends a proxy read request 84 to anotherstorage unit of the set of storage units that is not in the readthreshold number of storage units. For instance, the particular storageunit identifies the other storage unit based on one or more of: anindication within the respective read request, the read threshold numberof read requests including slice names that identified the readthreshold number of encoded data slices, by executing a distributedagreement protocol function, and by a look up table.

For example, in FIG. 9, SU #4 determines that it is not capable ofprocessing the respective read request of the read requests 82. SU #4selects SU #6 (a storage unit outside the read threshold number ofstorage units) as the other storage unit to send a proxy read request84. The other storage unit (SU #6) then determines whether it is capableof processing the respective read request. When SU #6 is capable ofprocessing the proxy read request, SU #6 processes the proxy readrequest 84.

As an example, the other storage unit (e.g., SU #6) processes the proxyread request by retrieving another encoded data slice of the set ofencoded data slices that was not included in the read threshold numberof encoded data slices from its local memory and sends it to the DSclient module 34. The other storage unit (e.g., SU #6) may alternativelyprocess the proxy read request by retrieving another encoded data sliceof the set of encoded data slices that was not included in the readthreshold number of encoded data slices from a local memory and send itto the particular storage unit (e.g., SU #4) so that the particularstorage unit can forward the other encoded data slice to the requestingcomputing device. If the other storage processes the proxy read requestand sends it back to the particular storage unit, it is beneficial toselect the other storage unit as one that is in close proximity to theparticular storage unit, as this can reduce the total round trip time ofthe proxy read request. Note that the other storage unit (e.g., SU #6)or the particular storage unit (e.g., SU #4) may notify the requestingcomputing device (e.g., DS client module 34) of the proxy read request.

When the other storage unit is not capable of processing the proxy readrequest, the other storage unit sends the proxy read request to yetanother storage unit of the set of storage units that is not in the readthreshold number of storage units. For example, if SU #6 determined thatit was not capable of processing the proxy read request 84, SU #6 sendsthe proxy read request 84 to SU #7, another storage unit that is not inthe read threshold number of storage units. The yet another storage unit(e.g., SU #7) then determines whether it is capable of processing theproxy read request. When it is capable of processing the proxy readrequest, the yet another storage unit processes the proxy read request.The other storage unit (e.g., SU #6), the particular storage unit (e.g.,SU #4), or the yet another storage unit (e.g., SU #7) may notify therequesting computing device that the proxy read request is beingprocessed by the yet another storage unit.

FIG. 10 is a logic diagram of an example of a method of sending a proxyread request within a dispersed storage network (DSN). The method beginswith step 88 where a read threshold number of storage units of the setof storage units of the DSN receive a read threshold number of readrequests regarding the read threshold number of encoded data slices of aset of encoded data slices where a data segment of a data object isdispersed storage error encoded into the set of encoded data slices, andthe set of encoded data slices is to be stored in the set of storageunits. The read threshold number is less than a total number of encodeddata slices in the set of encoded data slices and is equal to or greaterthan a decode threshold number. The read threshold number of encodeddata slices is a number of encoded data slices per set of encoded dataslices to be read from storage for decoding of the data segment. Thedecode threshold number is the number of slices of encoded data slicesof a set of encoded data slices that are needed to recover the datasegment.

The method continues with step 90 where each storage unit of the readthreshold number of storage units determines whether it is capable ofprocessing a respective read request of the read threshold number ofread requests. For example, a storage unit of the read threshold numberof storage units may determine that it is not capable of processing therespective read request if it determines that it does not currentlystore an encoded data slice identified in the respective read request.The storage unit may determine that it does not currently store anencoded data slice identified in the respective read request by one ormore of performing a table lookup, attempting to recover the encodeddata slice from a local memory, and attempting to recover the encodeddata slice from a non-local memory. As another example, a storage unitof the read threshold number of storage units may determine that it isnot capable of processing the respective read request if it determinesthat the encoded data slice identified in the respective read request isstored in a memory device of the particular storage unit that iscurrently unavailable. The storage unit may be unavailable due to afailure, or storage unit replacement and/or maintenance. Further, astorage unit of the read threshold number of storage units may determinethat it is not capable of processing the respective read request if itdetermines that processing of the respective read request would exceed aresponse time threshold.

When each storage unit of the read threshold number of storage unitsdetermines that it is capable of processing a respective read request ofthe read threshold number of read requests, the method continues withstep 92 where the storage units process the read requests normally. Whena particular storage unit of the read threshold number of storage unitsis not capable of processing the respective read request, the methodcontinues with step 94 where the particular storage unit sends a proxyread request to another storage unit of the set of storage units that isnot in the read threshold number of storage units. The particularstorage unit identifies the other storage unit based on one or more of:an indication within the respective read request, the read thresholdnumber of read requests including slice names that identified the readthreshold number of encoded data slices, by executing a distributedagreement protocol function, and by a look up table.

The method continues with step 96 where the other storage unitdetermines whether it is capable of processing the proxy read request.For example, the other storage unit may not be capable of processing therespective read request when it does not currently store the encodeddata slice identified in the respective read request, is unavailable dueto or maintenance, or processing would exceed a response time threshold.When the other storage unit is capable of processing the respective readrequest, the method continues with step 98 where the other storage unitprocesses the proxy read request. The other storage unit may process theproxy read request by retrieving another encoded data slice of the setof encoded data slices that was not included in the read thresholdnumber of encoded data slices from a local memory, and sending the otherencoded data slice to a requesting computing device. The other storageunit may alternatively process the proxy read request by retrievinganother encoded data slice of the set of encoded data slices that wasnot included in the read threshold number of encoded data slices from alocal memory and send it to the particular storage unit so that theparticular storage unit can forward the other encoded data slice to therequesting computing device. The other storage unit or the particularstorage unit may notify the requesting computing device of the proxyread request.

When the other storage unit is not capable of processing the proxy readrequest, the method continues with step 100 where the other storage unitsends the proxy read request to yet another storage unit of the set ofstorage units that is not in the read threshold number of storage units.The method continues with step 102 where the yet another storage unitdetermines whether it is capable of processing the proxy read request.When it is capable of processing the proxy read request, the methodcontinues with step 104 where the yet another storage unit processes theproxy read request. The other storage unit, the particular storage unit,or the yet another storage unit may notify the requesting computingdevice that the proxy read request is being processed by the yet anotherstorage unit.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method comprises: receiving, by a readthreshold number of storage units of a set of storage units of adispersed storage network (DSN), a read threshold number of readrequests regarding a read threshold number of encoded data slices of aset of encoded data slices, wherein a data segment of a data object isdispersed storage error encoded into the set of encoded data slices,wherein the set of encoded data slices is stored in the set of storageunits, and wherein the read threshold number is less than a total numberof encoded data slices in the set of encoded data slices and is equal toor greater than a decode threshold number; determining, by each storageunit of the read threshold number of storage units, whether the storageunit is capable of processing a respective read request of the readthreshold number of read requests; when a particular storage unit of theread threshold number of storage units is not capable of processing therespective read request: sending, by the particular storage unit, aproxy read request to another storage unit of the set of storage unitsthat is not in the read threshold number of storage units; determining,by the other storage unit, whether the other storage unit is capable ofprocessing the proxy read request; and when the other storage unit iscapable of processing the proxy read request, processing, by the otherstorage unit, the proxy read request.
 2. The method of claim 1, whereinthe determining whether the storage unit is capable of processing therespective read request comprises one or more of: determining that thestorage unit does not currently store an encoded data slice identifiedin the respective read request; determining that the encoded data sliceidentified in the respective read request is stored in a memory deviceof the particular storage unit that is currently unavailable; anddetermining that processing of the respective read request would exceeda response time threshold.
 3. The method of claim 1 further comprises:identifying, by the particular storage unit, the other storage unitbased on one or more of: an indication within the respective readrequest; the read threshold number of read requests including slicenames that identified the read threshold number of encoded data slices;by executing a distributed agreement protocol function; and by a look uptable.
 4. The method of claim 1, wherein the processing of the proxyread request comprises: retrieving, by the other storage unit, from alocal memory another encoded data slice of the set of encoded dataslices that was not included in the read threshold number of encodeddata slices; and sending, by the other storage unit, the other encodeddata slice to a requesting computing device.
 5. The method of claim 1,wherein the processing of the proxy read request comprises: retrieving,by the other storage unit, from a local memory another encoded dataslice of the set of encoded data slices that was not included in theread threshold number of encoded data slices; sending, by the otherstorage unit, the other encoded data slice to the particular storageunit; and forwarding, by the particular storage unit, the other encodeddata slice to a requesting computing device.
 6. The method of claim 1further comprises: notifying, by the particular storage unit or theother storage unit, a requesting computing device of the proxy readrequest.
 7. The method of claim 1 further comprises: when the otherstorage unit is not capable of processing the proxy read request:sending, by the other storage unit, the proxy read request to yetanother storage unit of the set of storage units that is not in the readthreshold number of storage units; determining, by the yet anotherstorage unit, whether the yet another storage unit is capable ofprocessing the proxy read request; and when the yet another storage unitis capable of processing the proxy read request, processing, by the yetanother storage unit, the proxy read request.
 8. The method of claim 7further comprises: notifying, by the particular storage unit, the otherstorage unit, or the yet another storage unit, a requesting computingdevice of the proxy read request being processed by the yet anotherstorage unit.
 9. A computer readable memory device comprises: a firstmemory section that stores operational instructions that, when executedby a read threshold number of storage units of a set of storage units ofa dispersed storage network (DSN), causes the read threshold number ofstorage units to: receive a read threshold number of read requestsregarding a read threshold number of encoded data slices of a set ofencoded data slices, wherein a data segment of a data object isdispersed storage error encoded into the set of encoded data slices,wherein the set of encoded data slices is stored in the set of storageunits, and wherein the read threshold number is less than a total numberof encoded data slices in the set of encoded data slices and is equal toor greater than a decode threshold number; a second memory section thatstores operational instructions that, when executed by each storage unitof the read threshold number of storage units, causes each storage unitof the read threshold number of storage units to: determine whether thestorage unit is capable of processing a respective read request of theread threshold number of read requests; a third memory section thatstores operational instructions that, when executed by a particularstorage unit of the read threshold number of storage units, causes theparticular storage unit to: send a proxy read request to another storageunit of the set of storage units that is not in the read thresholdnumber of storage units when the particular storage unit is not capableof processing the respective read request; a fourth memory section thatstores operational instructions that, when executed by the other storageunit, causes the other storage unit to: determine whether the otherstorage unit is capable of processing the proxy read request; and whenthe other storage unit is capable of processing the proxy read request,process the proxy read request.
 10. The computer readable memory deviceof claim 9, wherein the second memory section further stores operationalinstructions that, when executed by each storage unit of the readthreshold number of storage units, causes each storage unit of the readthreshold number of storage units to determine whether the storage unitis capable of processing the respective read request by one or more of:determining that the storage unit does not currently store an encodeddata slice identified in the respective read request; determining thatthe encoded data slice identified in the respective read request isstored in a memory device of the particular storage unit that iscurrently unavailable; and determining that processing of the respectiveread request would exceed a response time threshold.
 11. The computerreadable memory device of claim 9, wherein the third memory sectionfurther stores operational instructions that, when executed by theparticular storage unit, causes the particular storage unit to:identifying, by the particular storage unit, the other storage unitbased on one or more of: an indication within the respective readrequest; the read threshold number of read requests including slicenames that identified the read threshold number of encoded data slices;by executing a distributed agreement protocol function; and by a look uptable.
 12. The computer readable memory device of claim 9, wherein thefourth memory section that stores operational instructions that, whenexecuted by the other storage unit, causes the other storage unit toprocess the proxy read request by: retrieving from a local memoryanother encoded data slice of the set of encoded data slices that wasnot included in the read threshold number of encoded data slices; andsending, by the other storage unit, the other encoded data slice to arequesting computing device.
 13. The computer readable memory device ofclaim 9 further comprises: the fourth memory section further storesoperational instructions that, when executed by the other storage unit,causes the other storage unit to process the proxy read request by:retrieving from a local memory another encoded data slice of the set ofencoded data slices that was not included in the read threshold numberof encoded data slices; sending the other encoded data slice to theparticular storage unit; and the third memory section further storesoperational instructions that, when executed by the particular storageunit, causes the particular storage unit to: forward the other encodeddata slice to a requesting computing device.
 14. The computer readablememory device of claim 9, wherein the third or fourth memory sectionfurther stores operational instructions that, when executed by theparticular storage unit or the other storage unit, causes the particularstorage unit or the other storage unit to: notify a requesting computingdevice of the proxy read request.
 15. The computer readable memorydevice of claim 9 further comprises: the fourth memory section furtherstores operational instructions that, when executed by the other storageunit, causes the other storage unit to: send the proxy read request toyet another storage unit of the set of storage units that is not in theread threshold number of storage units when the other storage unit isnot capable of processing the proxy read request; a fifth memory sectionthat stores operational instructions that, when executed by the yetanother storage unit, causes the yet another storage unit to: determinewhether the yet another storage unit is capable of processing the proxyread request; and when the yet another storage unit is capable ofprocessing the proxy read request, process the proxy read request. 16.The computer readable memory device of claim 15, wherein the third,fourth, or fifth memory section further stores operational instructionsthat, when executed by the particular storage unit, the other storageunit, or the yet another storage units, causes the particular storageunit, the other storage unit, or the yet another storage unit to: notifya requesting computing device of the proxy read request being processedby the yet another storage unit.